Engine oil (again) + warming up

The BMW shop that put in my new used engine (<100K miles) told me to run 15w50 synthetic this winter because it was "an older engine". Why would that be? I know there's a lot of different philosophies out there about oil, but what's the rationale in this case? He said just to warm it up longer when it's real cold out.

BTW, the manual says that warming up the engine is not necessary except on the very coldest days. How long do you tend to warm up during the winter? During the other seasons?

I don't think it really matters what oil you put in as long as it's an appropriate grade for the weather. I've found 10W-40 to work great year-round.

As far as warming up goes, I just start to drive. It'll warm up eventually. My engine takes forever to warm up in the winter though; I could be 75% on the way to work and it would just be starting to blow warm air through the vents (I work 7 miles away, 90% highway travel). When I get on the highway, my engine is still cold and in final gear, it will rev more than 2k RPM for me to stay with traffic, so keeping it under 2k while the engine is cold isn't an option. But, if I let the car sit there while idling to warm it up, it takes well over double the time to warm up than if I just drive it, so driving it is much better anyway.

I've never heard that you don't need to warm the engine up before taking off. It was my understanding that you have the keep the revs below 2k until it's warmed up to prevent damaging the engine?

I've heard that your not supposed to let your car warm-up, just take-off like you said and it seems to work pretty well for me. School is only a mile away so of course its not warm by the time I get there but it only takes maybe 3 or 4 miles until it blows warm air, so i just go easy on the accelerator until my temp gauge is out of the blue temp indicator.

I just let it idle for about ten seconds before taking off, then stay below 3000 RPM until out of blue...... and below 4500RPM before fully warm... ;-)

He may have wanted you to use a thicker oil due to te fact that the seals are old and could start to leak. Personally, if a different grade oil is the difference between a failed gasket, I'll replace it anyways.